This invention relates to a speech synthesizer for using Speech Analysis and Synthesis of linear predictive coding techniques representing the PARCOR (PARTIAL AUTOCORRELATION) technique.
A recent speech synthesizer uses a fixed frame length, namely a fixed renew frequency of speech parameter at the synthesizing time and is intended to decrease information required at the synthesizing time so that the speech synthesizer is realized in one chip LSI.
The interpolation process which makes speech parameter in the frame change is executed so as to smooth the change of speech parameter in dependence on the time. It is required that the frame period is short so as to smooth the change of speech parameter in dependence on time in order to obtain good sound quality.
In this aspect, the conventional speech synthesizer does not attain sufficiently synthesized speech. There is a variable frame length technique as the approach of the speech synthesizer of PARCOR technique. In the variable frame length, one pitch of voiced sound including at least one pitch is a fundamental time and the frame interval is changed in dependence on the change of pitch length.
It is advantageous that the variable frame length may obtain better synthesized speech sound, but it is the problem that it makes information required in speech synthesis increase.